Process of roasting fusible ores.



No. 866,580. PATENTED SEPT. 17, 1907.

A. G. DAVIS. v

PROCESS OF ROASTING PUSIBLE ORES. APPLIOATION FILED 8E1T.12,.1896.

A BERT GOULD DAVIS, OF WASHINGTON, DISTRICT OF COLUMBIA PROCESS OF ROASTING FUSIBLE GEES.

Specification of Letters Patent.

' Patented Sept. 17, 1907.

Application filed September 12,1896. Serial No. 606,625.

To all whom it may concern:

lie it known that I, ALBERT Goutn DAVIS, a citizen of the United States, residing at Washington, in the District of Columbia, have invented certain new and useful Improvements in Processes of Roasting .Fusible Ores, of which the following is a specification.

My invention relates to the removal from ores of certain impurities, particularly sulfur. A large supply of oxygen is essential to the thorough desulfurization of ores. If a piece of FeS be heated in a mattrass to a high temperature, it will give off about one half of its sulfur as vapor, and there the operation will cease; even if the mattrass be heated to temperatures far above those which can be employed in commercial roasting, there will be a strong tendency to retain the last atom of sulfur, and for the resulting compound to be, practically, FeS. If now a similar piece of FeS be heated in an open tube with air passing over it, the sulfur will be driven off, and an oxid of iron will remain.

Ores of copper, and many other ores in commercial use, contain large percentages of sulfur, sometimes existing as FeS mechanically combined with the ore, and

in most cases occurring as compounds which, although more complex, are of the same order, that is to say are high in sulfur and fusible. It has been proposed to roast such ores by heating them to high temperatures in an oxidizing flame, and passing cold air across them when the temperature attained was so high that there was danger of fusion. successful on many ores, such as certain ores of iron in which the percentage of sulfur is low, and will Work well up to five per cent. of sulfur, or even more. But above a certain percentage air ceases to cool the ore, as the heat liberated chemically by the combustion of the sulfur and iron with the oxygen of .the air is greater than that absorbed in dissociating the FeS and mechanically abstracted by the cool air. Such ores may be said to burn with their own heat, and for such this process fails. If however the FeS remaining in the mattrass, in the experiment above described, be examined, it will be found to be porous, filled with openings where the sulfur has boiled out, and also highly infusible. FeS we substitute ores as of copper, high in sulfur, though the reaction in that case may not be so simple. To treat such ores I therefore use a double process; I first heat them above the boiling point of sulfur, in a practically closed chamber at an even temperature and in a reducing flame, orat least in the nearly complete absence of free oxygen. Part of the sulfur boils off, leaving a porous infusible compound of the FeS order. The ore cannot fuse during this stage of the process, as the temperature is too low and oxygen is carefully excluded. But when this stage is over the ore is in a condition where it ceases to burn with its own heat, and where it may be safely exposed to high term- This process is commercially The same condition will be observed if for peratures and oxidizing flames. I therefore now pass over or through it, preferably the latter, a current of highly heated gases containing an excess of oxygen, which rapidly burn out the remaining sulfur and leave oxide of iron and of sulfur. The latter are carried off by a suitable draft arrangement, and the oxide of iron, which constitute with the various substances mixed with them the roasted ore, are withdrawn.

7 Though I have described this process as applied to ores containing the sulfid of iron, it is not limited to that use, but applies to any substance whatever which possesses the characteristics above described.

Though the process may be carried on intermittently, great advantages result from making it continuous, and I have described a kiln for the purpose.

In the first stage of the process above described it is important that the temperature be fairly even and uniform; I therefore prefer to pass the gases which carry the heat to the ore in this stage through a chamber filled with broken stone or fire brick, checker work, or other substance capable of withstanding the temperatures used, and of absorbing and giving up heat. This also tends to give more perfect combustion.

My invention therefore consists in a process of roasting fusible ores containing sulfur or other oxidizable material which consists in exposing them first to a reducing flame and then to an oxidizing flame. Or, in other words, my invention consists in a process of treating ores which containwithin themselves a material (in the particular case above described, sulfur) which requires a certain chemical agent (in the case described, oxygen) for its complete removal, but which nevertheless will not endure without danger, the presence of the said chemical agent at the preferred temperatures, which consists in first removing a portion of'the said material, in the complete absence, or in the sufficient absence to secure the result desired, of said agent, and thereby changing the character of the ores in such a way that they can thereupon safely endure the presence of the said chemical agent at the preferred temperatures; and thereafter removing by the action of the said agent, part or all of the said material,

It also comprises a method of equalizing the temperature of a roasting furnace which consists in passing the gases from the combustion chamber through a mass of material capable of absorbing and giving out heat.

In the drawings annexed to this specification, Figure 1 is an elevationseetion of my improved kiln on the line 11 of Fig. 2. Fig. 2 is a half horizontal cross section on the line22 of Fig. 1.-

In the figures, 11, 12, and 13 are circular walls, inclosing the exit chamber 14, the ore chamber 15, and the upper combustion chamber 16.

17 is a circular wall inclosing the lower part of the chamber 16, while the annular space 18 between the walls 17 and 13 is the lower combustion chamber.

Gas is admitted to the arches 19, 20, by the flues 21, 22, respectively, and burns in the arches and combustion chambers. The arch l9 communicates with the chamber lb, while the arch 20 communicates with the chamber 18. Air is admitted through the doors 23, 24, and also if desired through the air flues 25, 26. The flues 25, 26, may be supplied with air under pressure, but I prefer to simply lead them to the outer air, and provide them with valves 25, 26. The gas fiues are piped to a suitable source of gas, and preferably provided with cleaning doors 21, 22, and suitable valves. The ore is fed at the top, in'the space 27, and passes through the ore space 15, being drawn out at the chutes 28. r

The two combustion chambers are separated from. each other by the wall 17, and the hopper 29, while they communicate with the ore space through the ports 30, 31. The ore space is connected with theexit space 14 by the ports 32 in the wall 12, 4 I

Gas burns at the arch 19 with a small amount of air, producing a strongly reducing flame, which passes through the checker work 35 to the chamber 16, through the upper portion of the ore space 15, through the ports 32 t0 the exit space 14, and thence through the ports 33, 33, to the collection flue 34, and thence to the draft stack. The checker work serves the purpose of equalizing the temperature of the burned and burning gases, aids combustion by setting up eddy currents, and prevents any irregularity of heat in different parts of the upper portion of the ore space. This latter effect is important, as the ore is there in its most fusible condition. Gas also burns at the arch 20,- but in this arch it is supplied with an exccssof air, giving an oxidizing flame, which passes through the chamber 18, thence through the ports 30, the ore space 15, and out as before.

Though I prefer to burn gas, as it is very easy to regulate and control, any other fuel, as oil,-coal, or wood, may be employed with suitable changes in the fire arches 19 and 20.

It is obvious that the collected gases contain large amounts of sulfur, which may be collected and used for the manufacture of sulfuric acid and for other purposes. As the gases resulting from the two stages of the process are of different chemical compositions, I may divide the exit chamber into two or more horizontal divisions as indicated by the dotted lines 40, and take the different mixtures out separately.

Cleaning arches, as 36, are provided where required, and the exit space 14 is provided with cleaning ports 37. The space at the top is preferably closed by the cone 38, and the whole kiln should be surrounded by a wrought iron or steel shell 39, with a proper expansion space as shown.

It should be distinctly understood that I do not limit myself to the use of a reducing atmosphere in the first stage of the process, as a small quantity of oxygen, though objectionable in most cases, is not necessarily fatal to the process.

Though it is preferable to use a highly heated gas in the last half of the process, it is not essential; as mere exposure of the heated ore to a current of air will remove large quantities of the remaining sulfur.

Although I have herein shown a particular form of roasting furnace well adapted for practicing the process herein described I do not claim the same in this application but reserve it for a co-pending divisional application filed in accordance with the Rulesof Practice of the United States Patent Ofiice.

I therefore donot limit myself to the particular forms shown and described, but claim as my invention,

L 'lhe process .of roasting fusible ores which consists in exposing them first to a high temperature in a reduclng atmosphere and thereby preventing fusion, and then to an oxidizing gas, substantially as described.

2. The process of roasting fusible ores containing sulfur which consists in exposing them first to a. reducing flame and then to an oxidizing flame, substantially as described.

3. The process of roasting fusible ores containing sulfur which consists in exposing them to a high temperature.

in a reducingntmosphere, distilling oif'a portion of the sulfur, and thereafter driving off more of the sulfur by the action of an oxidizing gas, substantially as described.

4. The process of roasting fusible ores containing sulfur which consists in exposing them to practically nonoxidizing combustion products at a .temperature sufflciently high to distil off a portion of the sulfur, and thereafter driving off more of the sulfur by subjecting them to the action of oxidizing gases at a high temperature, substantially as described.

5 .The process of roasting fusible ores which consists in passing them slowly through a narrow chamber, and passing across the chamber and through the ore successively at different points two currents of gas, first one containing little or no free oxygen, and being at a temperature sutficiently high to distilpff a portion of the volatile products in the ore, and thereafter one containing an excess of oxygen, substantially as described.

6. The process of roasting fusible ores which consists in passing them slowly by their own weight through a narrow substantially vertical ore chamber, and passing across the chamber and through the ore at different points two currents of gas, one containing little or no free oxygen and being at a temperature sufficiently high to drive off volatile matter in the ore; and the other current, which is introduced belowthe said first current, being at a high temperature and containing an excess of oxygen, substantially as described.

7. The process of roastingfusible ores containing sulfur which consists in heating them to a temperature above the point-at which they begin to give off sulfur, in a reducing atmosphere, and thereafter exposing them'to the action of an oxidizing gas, substantially as described.

8. The process of roasting fusible-ores containing'such quantities of oxidizable material as to cause them to oxidizing gasfsubflame, passing the products of combustion through or i across masses 'of material capable of absorbing and giving out heat and then into the ore space and thereafter passing an oxidizing gas-into a portion of said ore space so as to act on the ore after it is actedupon by the firstmentioned products of combustion.

10. The process of roasting fusible ores which consists in passing the ore through a'conflned ore space, burning fuel-with such amounts of air as will give a practically non-oxidizing'iiame, passing the products of combustion through or across masses of material capable-of absorbing and giving out heat, and thence into and across said orespace, and passing into and across said ore space at a lower part thereof an oxidizing gas at a hightemperature, substantially as described.-

11. The method of removing sulfur and similar material from ore, which consists in"assing the ore, in a substantially continuous operation, hrough spaces where it is exposed successively to two distinct currents of heated gas, first a substantially non-oxidizing gas, and second an oxidizing gas.

12. The method of roasting fusible ore, which consists in generating a substantially non-oxidizing gas of high temperature and another body of oxidizing gas of high temperature, exposing the ore to the action of the firstnamcd gas, and subsequently exposing it to the action'of the second-named gas.

13. The method of roasting ores which consists in burning carbon or carbon products with air to produce a body of hot combustion products, burning more carbon or carin passing a sulfur-bearing ore in a substantially con- I tinuous operation through a space occupied by a hot gas formed by the combustion of a heabproducing substance with a small quantity of oxygen, whereby fusion of the ore is prevented.

15. The method of roasting ores containing high percentages of sulfur which consists in exposing them by a continuous process, first to the action of combustion prod ucts containing large percentages of non-oxidizing gas and sufliciently small percentages of oxidizing gas to prevent them from burning with their own heat until they have been modified in their chemical structure, and thereafter exposing them to the action of an oxidizing gas at a high temperature and thereby removing part or all of their sulfur.

16. The method of roasting ores whlch consists in feeding theore through an ore space, passing currents of hot gas across the ore space, regulating one of the gas currents so as to be low in free oxygen, and regulating another gas current so as to have a considerably larger percent age of free oxygen, and exposing the ore to the action of the gasesin the order named.

In witness whereof I have hereunto signed my name this 12th. day of September, in the year 1896, in the presence of two witnesses.

ALBERT GOULD DAVIS.

Witnesses F. G. HOPKINS, R. 1). WHITE. 

